What you are talking about has to do with your red blood cell counts or rbcs.
They carry oxygen
to your tissues. If your rbcs are too low, that's call anemia
. There a few kinds of anemia but we need more information to advise you what you might needs. Commomly, rbcs low as a consequence of iron
deficiencies. There is now a simple way to determine the oxygen in the blood. See the doctor.